Distribution Of Sedimentary Environments Research Articles

Sedimentary characteristics of 1st member of Yaojia Formation in Zhaoyuan-Taipingchuan region of Songliao Basin

Through integral studies on cores, seismics, well-logs and laboratory sediment analysis a new sequence stratigraphic framework of the Late Cretaceous first member of the Yaojia Formation in the Songliao Basin, in China's Zhaoyuan-Taipingchuan (Zhy-Tpch) region, has been reconstructed. In this study, the first member of Yaojia Formation is divided into 3 three-order depositional sequences, each composed of three systems tracts, i.e. the lowstand systems tract (LST), the transgressive systems tract (TST) and the highstand systems tract (HST). Using a dense network of cored boreholes data and data acquired from a combination of spontaneous potential and electric resistivity logging methods, the paper studies the characteristics and distribution of sedimentary environments within the cyclic patterns (systems tracts) of the major depositional sequences, and ascertains that deposition of sediments in a predominantly shallow lake delta environment which prevailed in the region during the Late Cretaceous period was responsible for the creation of the first member of the Yaojia Formation. Results show that this formation is mainly composed of three sub-facies namely, the delta plain, delta front and prodelta (the shore shallow lake). Each sub-facies is further subdivided into eleven sedimentary environments including distributary channels, natural levees, crevasse splays, inter-distributary channels, flood plains, subaqueous distributary channels, inter-distributary bays, subaqueous crevasse splays, mouth bars, distal bars and sheet sands. The delta plains and delta fronts are widely developed. Deposited with frequent bifurcations, the distributary channels gradually moved towards the center of the lacustrine basin where prodelta sedimentation had hardly occurred. Meanwhile, subaqueous channels were frequently developed within the shallow water areas of the delta fronts. Sandstone facies in the distributary and subaqueous distributary channels mutually interacted and stacked up to form dendritic-like sands. Distributary channel sands formed the most favorable reservoirs available today and are considered to be the most important exploration targets for the oil industry. Overall, this study is crucial for improving the understanding of the geological and paleo-geographic record in the Zhy-Tpch region including the facies types, relationships and cyclicity in response to changes in depositional environments (i.e. sedimentation and base-level changes) that prevailed in the region during the Late Cretaceous period and hence important for the predictive aspects of the economic petroleum exploration and development in the Songliao Basin.

Geotechnical Influence on the Acoustic Properties of Marine Sediments of the Santos Basin, Brazil

There are several problems associated with core location and sediment deformation during the coring procedure. Geophysical investigation of the seafloor using acoustic systems, such as high-resolution seismic and single-beam sediment classification, provides a very cost-effective evaluation on the distribution of sedimentary environments. The present study investigates the relationship between acoustic impedance and geotechnical properties of shallow marine sediments from the Santos Basin, Brazil. A total of eight cores from different geological settings were collected and measurements of P-wave velocity (Vp), gamma density, mean grain size, void ratio, water content and shear strength were conducted. The results show that, despite different trends according to the sedimentary environment, the acoustic impedance correlates very well with all geotechnical parameters analyzed.

Development of carbonate platforms on an extensional (rifted) margin: the Valanginian–Albian record of the Prebetic of Alicante (SE Spain)

Within the upper Valanginian to upper Albian deposits of the easternmost part of the Prebetic Zone of the Betic Cordillera (Iberian Peninsula), seven lithostratigraphic formations made up of shallow-water carbonate and carbonate-siliciclastic sediments and of outer-platform hemipelagic sediments have been recognized. These formations were deposited in the most distal part of a platform that developed on the Southern Iberian Continental Palaeomargin. The geodynamic context was a margin affected by extensional or transtensional faults that produced tilted blocks. The interval studied records three major second-order transgressive-regressive facies cycles: (I) A late Valanginian to earliest Aptian cycle, mostly represented by hemipelagic and condensed sedimentation, with the development of a tectonically controlled high without sedimentation that separated two sectors with different sedimentary evolution and that ended with an episode of shallow-water carbonate platform development; (II) An earliest to latest Aptian cycle, with a transgressive phase represented by a retrogradational shallow-water carbonate platform capped by a drowning event leading to hemipelagic sedimentation, which was affected by an anoxic event (OAE 1a); the regressive phase is represented by progradation and aggradation of shallow-water carbonate deposits. Finally (III) a latest Aptian to early-late Albian cycle that records the expansion of mixed platform deposits in the entire area, ending with a phase of shallow-water carbonate platform development. Extensional tectonics leading to spatial and temporal changes in subsidence patterns is envisaged as the main control on sedimentation at a local scale, resulting in notable lateral changes in thickness as the main signature. Tectonics exerted a strong control on the distribution of sedimentary environments only during Cycle I. At a higher order, sea-level fluctuations are responsible for sequential organization, and environmental factors determined shallow-water carbonate platform development and demise, as well as oceanic anoxic events. The relevant continuity of the stratigraphic record in the distal part of the Prebetic platform has led to the recognition of events related to cycle boundaries, which result mainly from a combination of tectonics and sea-level changes.

Cybertectonic Earth and Gaia's weak hand: sedimentary geology, sediment cycling and the Earth system

Tectonics, climate and sea level are dominant controls on the nature and distribution of sedimentary environments. By inverse logic, recognition of influences on sedimentation from the stratigraphic record as a result of perturbations in these variables leads to clarification of past environmental and structural change. The succession of sedimentary environments in time and place is determined by a wider combination of variables; namely, sediment flux, biological evolution, atmosphere and water body productivity and chemistry. The feedbacks and interrelationships between all variables cause the complexity seen in sedimentation processes over geological time. The processes of global tectonics that cause widespread mountain belt and continental plateau uplift have produced numerous ‘severe’ events during Earth history: these often random workings-out of the plate tectonic cycle define the state of ‘Cybertectonic Earth’ (from cyber , after the Greek kubernan : to steer or govern). This has worked within a usually zonally arranged series of climatic belts and within the framework provided by biological evolution. At certain times in the geological past, a combination of factors arose as a response to continental uplift and have acted to cause certain Earth surface conditions and variables (notably mean global surface temperature, atmospheric p CO 2 , p O 2 ) to have varied by very large amounts (×2–×10) compared with present values. These large fluctuations, such as those responsible for the Neoproterozoic, Late Palaeozoic and late Tertiary glaciations, lead one to doubt the reality of homeostatic control of surface conditions as proposed in Lovelock's Gaia hypothesis. The Gaian kuberne0te0s (steersman) had a weak hand on the helm, frequently unable to prevent vast areas of the globe experiencing rapid fluctuations in environmental conditions and inimical conditions to life for very long periods during Neoproterozoic and Phanerozoic times. At the same time, biogenic and abiogenic processes have proved capable of returning Earth to states of mean stability, although biogeochemical cycling models seem alarmingly ad hoc and largely untestable as scientific hypotheses in any true geological sense.

Process-related classification of acoustic data from the Hudson River Estuary

Acoustic surveying provides valuable information on the distribution of sedimentary environments in subaqueous settings. Frequently, differences in acoustic backscatter strength are used to distinguish sedimentary environments on the basis of their grain size composition. Here, we are presenting acoustic backscatter data from the Haverstraw Bay section of the Hudson River Estuary that has been mapped using sidescan, sub-bottom profiling, and multibeam bathymetry as part of the Benthic Mapping Project of the Hudson River Estuary Program, funded by New York State. In addition, hundreds of gravity cores, and grab samples provide ground truth for a classification of the river bottom into discrete substrate types. Analyses of sedimentary environments reveal patterns in backscatter strength beyond those that can be related to the sediment grain size distribution alone. An integrated interpretation of sidescan, sub-bottom profiling, and high-resolution bathymetry data indicates that the backscatter pattern can be attributed to spatial variations in the modern depositional environments which cause differences in bottom roughness and sediment compaction. Based on an integrated interpretation of the acoustic and sample data sets, we distinguished eight different sedimentary classes. Many of the classes can be linked to dynamic processes including contemporary deposition, erosion, and sediment migration in sand waves. The results provide a better understanding of the dynamic processes of the Hudson River Estuary and improve the interpretation of the acoustic backscatter data from fine grained sedimentary environments.

The tectonic factor in sea level change: A countervailing view

It is now demonstrable that many unconformity‐bounded assemblages of strata, the sequences and groupings of sequences of seismic stratigraphy, can be correlated subglobally. The facies tracts that are identifiable within sequences clearly represent depositional environments that bear a systematic relationship to the strandline and to water depths, and thus to sea levels. Lacking a more suitable explanation for the intercontinental correlation of sequences it has become widely accepted that eustatic changes of sea level are responsible for the interruptions in sedimentation that separate sequences and for the shifts of coastal onlap and of facies tracts implicit in sequence analysis. Students of cratonic basins are convinced that continental interiors are subject to a tectonic evolution of positive and negative vertical movements and that these control relative sea level and the distribution of sedimentary environments. Proof of this control is buried hi the sedimentary fills of cratonic basins, but it has been difficult to produce such proof in a form digestible by Neo‐Neptunist doubters. Digitization of isopach maps of successive stratal units produces thickness data amenable to numerical study. For example, the logarithms of thicknesses of a stratal unit commonly exhibit a uniform areal distribution, the hallmark of a bivariate‐normal distribution. This revelation makes available a number of Gaussian statistical measures as descriptors of time‐variable basin geometry. Extraction and analysis of geometric parameters lead to the realization that basin evolution, necessarily including relative sea levels and the transgression and progradation of strandlines and sedimentary environments, has a strong tectonic component that gives evidence of synchrony of widely separated basins on separate cratons. Secular variation in radial heat flow, leading to episodic inflation and deflation of continents is suggested as a possible globally effective mechanism.

Sedimentology and paleogeography of some Kaihikuan Torlesse rocks in mid Canterbury

Abstract Three sedimentary facies are recognised within Fingers Formation, a stratigraphic unit of Kaihikuan age within the Torlesse terrane. A thick-bedded sandstone facies, which is most abundant, has features indicating deposition by high-concentration mass-flow processes, and it is interpreted as a submarine fan-channel deposit. Rocks of a subordinate thin-bedded flysch and siltstone facies are interpreted as relatively low-concentration turbidity current deposits and are inferred to be interchannel, proximal submarine fan deposits. A rare third facies, pebbly mudstone, most likely had a debris flow origin. It is concluded that Fingers Formation is a base-of-slope, proximal submarine fan deposit, in contrast to the more deep water, turbidite-rich Pudding Hill Formation to the east, and to the transgressive shallow shelf Mount Potts Group to the west, both of which are also of Kaihikuan age. The distribution of sedimentary environments during Kaihikuan time in mid Canterbury therefore suggests an east-...

Sedimentary Tectonics and Sedimentary Environments

The tectonic framework of sedimentation--basins, geosynclines, neutral areas, and positives--largely controls the distribution of sedimentary environments by its control of source areas, strand lines, and bathymetric zones. A major problem in distinguishing tectonic elements and tectonic intensity arises from the interplay between contemporaneous depositional subsidence, and intermittent uplift and erosion; and a major problem in evaluating environmental control arises from the time factor in the passage of sedimentary particles through the depositional interface. These problems and possible solutions are discussed in terms of a hypothetical cycle of deposition, in which tectonism, environment, and biological agencies are integrated in terms of their effects on the accumu ation of sediments. As a practical means of interpreting and designating the distribution of environments during a stratigraphic interval, a tectono-environmental classification is proposed, which includes groups of associated environments placed within a framework of increasing tectonic intensity. It is seen that the environmental impress on the sediments diminishes as a function of increasing tectonic intensity.